A child does 350J of work while pulling a box from the ground up to his tree house at a steady speed with a light rope. The tree house is 4.0 m above the ground. What is the mass of the box?

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Solution:

Given,

Work done = W = 350 J

Displacement = h = 4 m

Acceleration due to gravity = g =  9.8$m/s^2$

Formula used, Work done = Force * Dispacement

                        Work done = (mass*acceleration)*Displacement

                                      W=mgh

placing values, 350 = m*9.8*4

                           m = $\frac{350 J}{4m*9.8ms^{-2}}$

                           m =$\frac{350 J}{39.2m^{2}s^{-2}}$

                           m = 8.929 Kg

                           m = 8.9 Kg  (approx.)

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